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Spark plug

Active Publication Date: 2009-04-23
NGK SPARK PLUG CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0010]The present invention has been achieved to solve the above-noted problems. The invention provides a spark plug which can be configured to have a smaller diameter in comparison with conventional ones and to assure the vibration resistance and the connected portion with sufficient reliability.
[0057]According to one embodiment of the spark plug of the invention, the main metal fitting on the tip end side in view of the pressure detection sensor placement position has therein a heat release part which is in contact with the inner circumferential surface of the main metal fitting and the outer circumferential surface of the insulator, and the heat release part has a communicating portion for communications between the tip end side and the rear end side in the axial direction. Thus, the disturbance of the propagation of the combustion pressure by the heat release members can be prevented while keeping the heat radiation, and the combustion pressure can be measured with high sensitivity and precision.

Problems solved by technology

And, the spark plug having the main metal fitting and the insulator fixed by a welded connection, an adhesive connection, shrink fitting or the like can be made to have a small diameter but has not been put into practical use because it is hard to secure the vibration resistance and the connected portion with sufficient reliability.
One of the causes is a problem of airtightness whether the engine combustion chamber can be sufficiently kept airtight.
Then, there is a possibility of leaking a combustion / unburnt gas from the combustion chamber through a weakened connected portion.

Method used

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second embodiment

[0126]the invention will be described with reference to the drawings. FIG. 13 shows in a magnified fashion a cross section of the structure of a main portion of a spark plug 130 according to the embodiment of the invention, and FIG. 14 shows the entire appearance of the spark plug 130. The spark plug 130 is provided with the substantially cylindrical main metal fitting 1 and the substantially cylindrical insulator 2 which is fitted into the main metal fitting 1 so to project the tip end portion. As indicated by a dotted line in FIG. 13, the center electrode 3 having a copper core therein is disposed at the center portion of the tip end side in the insulator 2 along its axial direction, and the tip end portion of the center electrode 3 is projected from the tip end surface of the insulator 2. And, the ground electrode 10 is disposed to face the tip end portion of the center electrode 3. The ground electrode 10 has one end connected to the main metal fitting 1, and a spark discharge g...

third embodiment

[0139]Then, a third embodiment will be described with reference to FIGS. 16 to 19. FIG. 16 shows a state that the insulator is in a state before its attachment to the main metal fitting, and FIG. 17 shows an attached spark plug 140, where like component parts corresponding to those of the previous embodiment are denoted by like reference numerals, and overlapped descriptions will be omitted.

[0140]The main metal fitting 1 is formed of metal, for example, SUS630 (Vickers hardness of 455) or the like to have a cylindrical shape so to configure a housing for the spark plug 140, and a threaded portion 7 for attachment of the spark plug 140 to a not-shown engine block is formed on the outer circumferential surface of its tip end side (lower side of the drawing). A tool engagement portion 8 for engagement of a tool such as a spanner or a wrench to attach the main metal fitting 1 to the engine block is disposed on the outer circumference on a rear end side with respect to the threaded porti...

fourth embodiment

[0149]Then, a fourth embodiment will be described. FIG. 24 shows a state that the insulator is in a state before its attachment to the main metal fitting, and FIG. 25 shows the attached spark plug 160, where like component parts corresponding to those of the previous embodiment are denoted by like reference numerals, and overlapped descriptions will be omitted.

[0150]The main metal fitting 1 is formed of metal having a Vickers hardness (a value measured under a load of 10N according to a method specified in JIS Z2244 (1988)) in a range of 180 to 500, such as metal of SUS430, SUS630, S45C, S35C, SNCM439 or the like so to have a cylindrical shape. The Vickers hardness indicates a value obtained when the spark plug 160 is completed, and processing such as quenching, annealing or the like may be performed for adjustment after the work hardening or forming in the production process of the main metal fitting 1. The hardness may be measured with the spark plug 160 disassembled.

[0151]The met...

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Abstract

A spark plug 100, comprising a center electrode 3 which is extended in an axial direction, a cylindrical insulator 2 which holds the center electrode 3, and a cylindrical main metal fitting 1 which has a ground electrode 10 at a tip end portion and a tool engagement portion 8 for mounting on an engine, wherein the main metal fitting 1 has a part of a rear end side from the tool engagement portion 8 as a metal fitting-side fitting portion 9 and holds the insulator 2 in a tightly fitted state in a radial direction by the metal fitting-side fitting portion 9.

Description

TECHNICAL FIELD[0001]The present invention relates to a spark plug used for an internal combustion engine such as automobile engines.BACKGROUND ART[0002]It is known that a conventional spark plug has a structure provided with a center electrode, an insulator for holding the center electrode and a main metal fitting which is equipped with a ground electrode at its tip end portion and has a tool engagement portion for mounting on an engine, and the insulator is supported and fixed in the main metal fitting. Such a spark plug generally has a structure that the insulator is inserted into the main metal fitting having a cylindrical shape, and one end of the main metal fitting is caulked to support and fix the insulator in it (see, for example, Patent Reference 1).[0003]The insulator is cylindrical and has a large-diameter portion which is formed on the intermediate portion in the axial direction of the insulator to protrude in a radial direction to have a flange shape and a largest outer...

Claims

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Application Information

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IPC IPC(8): H01T13/16H01T13/20
CPCF02P13/00H01T21/02H01T13/36
Inventor HOTTA, NOBUYUKIKODERA, EIJIOHBAYASHI, KAZUSHIGESUGIMOTO, NORIYASU
Owner NGK SPARK PLUG CO LTD
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